The present invention relates to valves designed for use with Gerotor r otary machines which are used as fluid pumps or motors in which the fluid introduced is contracted and expanded by a meshing gear system generally known as a Gerotor, and more particularly the invention relates to a rotary valve including sealing means designed to prevent leakage of fluid caused between the high pressure side and the low pressure side of the commutator.
With a fluid motor or pump of the Gerotor type in which a rotor formed with one less external tooth than the number of internal teeth of a stator, is rotated in eccentric mesh with the stator and a pluralty of expanding and contracting cavities are defined by the teeth of the stator and the rotor in response to the eccentric rotation of the rotor, it has been the practice to use a rotary valve to selectively connect the fluid passages with the Gerotor cavities so that a hydraulic oil is supplied to impart a turning force to the rotor in the case of a fluid motor, while a hydraulic oil is discharged from the contracting Gerotor cavities in the case of a fluid pump.
With a known rotary valve of this type, due to the fact that the commutator is rotated within the valve chamber, a clearance which is as small as to not impede the rotation of the commutator is provided at each side of the commutator, and consequently there is a disadvantage that the oil tends to leak from the high pressure side to the low pressure side within the valve chamber, thus diminishing the volumetric efficiency of a motor or pump. As a result, the width of the clearance on each side of the commutator has been made very small so far as the rotation of the commutator is not impeded, thus requiring a high degree of machining accuracy for the component parts of the rotary valve. However, there is a disadvantage that even if the component parts with a high degree of accuracy are used, the clamping force of bolts or the like used in assembling the valve tends to distort the component parts of the valve chamber and moreover the existence of the high oil pressure portion and the low oil pressure portion within the valve chamber tends to similarly distort the component parts of the valve chamber by the pressure difference between the two portions, thus increasing the width of the clearance at each side of the commutator. In view of these circumstances, rotary valves of a construction in which the clearance at each side of a commutator is adjusted in response to the pressure difference in the valve and rotary valves of the construction which reduces distortion of the component parts have been proposed by the inventors, YOKOYAMA and TAKAMATSU, of the present invention as disclosed in Japanese Patent Application No. 67863/77 and No. 109940/77.